Best synthetic oil to use in a FC
 

New owner to a FC non-turbo and would like some advice on what the best synthetic oil would be for the car.
The car will be driven lightly.

Thanks!

There are about 10,000 oil threads on this forum, so a search for "synthetic oil recommendation" will likely turn up more reading than you would ever want, and every oil thread turns into a damn debate. :)

Basically, any quality oil (Mobile 1, Castrol, etc.) in the viscosity recommended by the service manual/owners manual for your climate.

CA is pretty warm, so I'd say 20W-50.

Saw some of the threads after I posted and it is a debate for sure.

Thanks for the reply though

Valvoline VR1 racing synthetic 20w50 (blue oil) has lots of zinc additives or Royal Purple 20w50 is what I use......

These are the ones that I have seen recommended so far:

Idemitsu Rotary Racing Engine Oil
Valvoline VR Racing oil 20w-50
Royal Purple 20w50
Pettit Racing's Revomax

Leaning towards Idemitsu or Valvoline at the moment.

Thanks for the feedback.

For a lightly-driven car, the only advantage of synthetic engine oil is that it would work well if your car is driven in extremely cold winter weather (10F below zero or colder). Otherwise, you will be wasting your money by using synthetic oil in the engine. Synthetic engine oil is mostly used by people who race their cars on a professional track. Castrol GTX non-synthetic oil has a great reputation for working well in rotary engines.

I do recommend synthetic oil in the transmission because it really helps smooth out the shifting, and you can also use synthetic oil in the differential. The extra cost of synthetic is not such a problem for the transmission and differential because the change interval is 60,000 miles / 60 months for a lightly-driven car. I prefer Red Line because it is made with Group V esther base stock as well as Group IV PAO, and it is usually less expensive than the other equivalent or lesser brands. However, I think that any of the other full-synthetic (Group IV and V base) brands are fine if you can get them for a good price. The only brand I have a problem with is Mobil One because their oil has been known to eat RX-7 transmission synchronizers, and they suspiciously refuse to tell consumers what kind of base stock is used in their oil. Rumor has it that they are using a lot of Group IIIa oil in the mix, which is just glorified mineral oil.

While 20W-50 would work just fine (especially during a heat wave), I think I would rather use 10W-40 to cut down on wear and hopefully increase gas mileage a bit. If he were a more aggressive driver then I would recommend the 20W-50.

There is still no evidence that the zinc level makes any difference in rotary engines. I guess it wouldn't hurt to use high-zinc oil just in case, but for now it has only been shown to make a difference in engines that have a valve train.

Evidences:
Zinc Oil Additive - Hot Rod Magazine

As far as the corrosion issue, aren't the factory iron bits plated (with chrome or cadmium or something)?

I dont use synthetic you have to be really careful putting synthetic in a rotary...Best to stick without sythetic and use conventional but a heavier weight depending on the season 20w50 is what i use..i have also used 10W30

+1 castrol gtx

Again, there is no mention of any measured difference with respect to a rotary engine. Likewise, there have been no reports of rotary engine damage or premature wear from people who are using the newer oil formulas. I am a member of SAE, so I keep looking for reports on this subject, but so far it seems like the rotary engine does not care much about the zinc content.

what about eneos and idemitsu? ive read a bit about htem, but havnt realy looked into much

Synthetic Oil
 

I spent a lot of time reading the synthetic oil debate on this site and couldn't make heads or tails of it. In asking questions of some local people while rebuilding my '84 GSL SE, I got a little bit of information that may or may not make sense, but it did for me.
The RX7's engine injects a little bit of oil while running into the motor to keep the apex seals, etc. lubricated. That oil comes from the car's oil. So using the oil that "burns" better and cleaner is the best oil to use. Made sense to me. Hope it makes a difference to you.

I've been using amsoil 20w50 in my rx7. when I took the engine apart after 50,000 miles the bearing had very little wear. When I disassembled a engine that used mobil 1 it was very clean but showed more bearing wear.

If you aren't running the motor hard, any oil that meets the viscosity requirements with a reasonable change interval will do fine.

How does 20w50 cause more wear? i always ran 20w50 castrol gtx in my old na.

I figured it gives more oil.pressure and gives better protection at high rpms, which is where you're going to be for spirited driving (most rx7 owners are spirited drivers).

However for regular street driving (shifting at 3-4k, occasionally redlining) im really not sure what is ideal after reading this.

Any feedback?

Context. If you go to the very top of this thread, you will see that the original poster stated "The car will be driven lightly." While heavier oil is generally more stable under high loading, it also generally causes more friction. This increased friction results in a little more heat and wear, and a little less power and gas mileage.

Back in the 1980s the 10W-40 grades of oil were not very stable, so 20W-50 was a better option for hot weather and aggressive driving. Modern 10W-40 is much more stable, which makes it a good choice for street driving and mild performance events like autocross. Those who drive very aggressively in hot weather are probably better off with 20W-50, especially in turbocharged applications. However, I should point out that Mazdaspeed Motorsports Development has recommended SAE 30 or 40 oil (mineral or synthetic) for racing since the 1990s. See page TT-22:
http://www.mazdaspeeddevelopment.com...g/techtips.pdf

*sigh*

people does all kinds of useless shit to their car/engine, and they're pussy about using Synthetic oil?

If it is just being driven lightly, I would save some money and buy whatever regular oil is on sale in the weight you need. I use castrol gtx 10W30 in my FD and I drive it like a jackass with no problems.

Thanks i never knew any of this, .great info.

After reading it im thinking 20w50 isnt really necessary, unless you're always in the top of your powerband (drifting/drag) ,

Or is it just not really a good option at all? Increased wear, heat, and reduced hp and gas mileage seem like alot of negatives and really don't outweigh the positives of increased oil pressure and being more stable at higher rpm loads.

Though i always thought more oil pressure was a good thing, so Im still slightly confused....

hmph..id think there are other ways to increase your oil pressure other than using a thicker/heavier oil.

+1 castrol gtx

or some good ol supertech from walmart....haha jk dont do that....10w30 castrol gtx

Yeah, I would suggest staying away from the synthetics unless you've done your research on how to mix them properly.

I must be evil, I use Synthetic with no problems !

Before any of you naysayers wanna throw yada yada yada at me, hey, I'm not gonna get into any argument, cuz after so many years, I know we will not have a conclusion.

But what I do know is

Mazda Japan sells Synthetic Oil to Rotary Engines.

:)

Redline, Royal Purple, Eneos, Mobil1 (0w40 only), Amsoil, no problems. :)

Mazda recommend those because one SAE grade is always more stable than multi-visocity grade oil. and SAW 30/40 is a good compromised between speed and protection. Don't forget, all they need is something that would allow them to pass the finish line.

they might recommend it since 1990s, but who knows what they're using now, they don't have to tell us everything, nor they have to keep their site always up to date.

20w50 might be a bit overkill for some people, but really most of us Rotary guys like to "Rev that mofo" for no reason ... and happens all the time, cuz we can (unlike a piston), so 20w50 is not a bad choice. But for people who lives up in the north (like Canada), 10w40 or 5w30 might work better.

I use 20w50 in NYC almost all year long, no issue, oh and I also use good Synthetic :) which flows better than any Mineral based oil even at the same rating.